package org.apache.lucene.analysis.standard;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.analysis.*;
import org.apache.lucene.util.IOUtils;
import org.apache.lucene.util.Version;

import java.io.File;
import java.io.IOException;
import java.io.Reader;
import java.util.Set;

/**
 * Filters {@link StandardTokenizer} with {@link StandardFilter}, {@link
 * LowerCaseFilter} and {@link StopFilter}, using a list of
 * English stop words.
 *
 * <a name="version"/>
 * <p>You must specify the required {@link Version}
 * compatibility when creating StandardAnalyzer:
 * <ul>
 *   <li> As of 3.4, Hiragana and Han characters are no longer wrongly split
 *        from their combining characters. If you use a previous version number,
 *        you get the exact broken behavior for backwards compatibility.
 *   <li> As of 3.1, StandardTokenizer implements Unicode text segmentation,
 *        and StopFilter correctly handles Unicode 4.0 supplementary characters
 *        in stopwords.  {@link ClassicTokenizer} and {@link ClassicAnalyzer} 
 *        are the pre-3.1 implementations of StandardTokenizer and
 *        StandardAnalyzer.
 *   <li> As of 2.9, StopFilter preserves position increments
 *   <li> As of 2.4, Tokens incorrectly identified as acronyms
 *        are corrected (see <a href="https://issues.apache.org/jira/browse/LUCENE-1068">LUCENE-1068</a>)
 * </ul>
 */
public final class StandardAnalyzer extends StopwordAnalyzerBase {

    /** Default maximum allowed token length */
    public static final int DEFAULT_MAX_TOKEN_LENGTH = 255;

    private int maxTokenLength = DEFAULT_MAX_TOKEN_LENGTH;

    /**
     * Specifies whether deprecated acronyms should be replaced with HOST type.
     * See {@linkplain "https://issues.apache.org/jira/browse/LUCENE-1068"}
     */
    private final boolean replaceInvalidAcronym;

    /** An unmodifiable set containing some common English words that are usually not
    useful for searching. */
    public static final Set<?> STOP_WORDS_SET = StopAnalyzer.ENGLISH_STOP_WORDS_SET;

    /** Builds an analyzer with the given stop words.
     * @param matchVersion Lucene version to match See {@link
     * <a href="#version">above</a>}
     * @param stopWords stop words */
    public StandardAnalyzer(Version matchVersion, Set<?> stopWords) {
        super(matchVersion, stopWords);
        replaceInvalidAcronym = matchVersion.onOrAfter(Version.LUCENE_24);
    }

    /** Builds an analyzer with the default stop words ({@link
     * #STOP_WORDS_SET}).
     * @param matchVersion Lucene version to match See {@link
     * <a href="#version">above</a>}
     */
    public StandardAnalyzer(Version matchVersion) {
        this(matchVersion, STOP_WORDS_SET);
    }

    /** Builds an analyzer with the stop words from the given file.
     * @see WordlistLoader#getWordSet(Reader, Version)
     * @param matchVersion Lucene version to match See {@link
     * <a href="#version">above</a>}
     * @param stopwords File to read stop words from */
    public StandardAnalyzer(Version matchVersion, File stopwords) throws IOException {
        this(matchVersion, WordlistLoader.getWordSet(IOUtils.getDecodingReader(stopwords, IOUtils.CHARSET_UTF_8), matchVersion));
    }

    /** Builds an analyzer with the stop words from the given reader.
     * @see WordlistLoader#getWordSet(Reader, Version)
     * @param matchVersion Lucene version to match See {@link
     * <a href="#version">above</a>}
     * @param stopwords Reader to read stop words from */
    public StandardAnalyzer(Version matchVersion, Reader stopwords) throws IOException {
        this(matchVersion, WordlistLoader.getWordSet(stopwords, matchVersion));
    }

    /**
     * Set maximum allowed token length.  If a token is seen
     * that exceeds this length then it is discarded.  This
     * setting only takes effect the next time tokenStream or
     * reusableTokenStream is called.
     */
    public void setMaxTokenLength(int length) {
        maxTokenLength = length;
    }

    /**
     * @see #setMaxTokenLength
     */
    public int getMaxTokenLength() {
        return maxTokenLength;
    }

    @Override
    protected TokenStreamComponents createComponents(final String fieldName, final Reader reader) {
        final StandardTokenizer src = new StandardTokenizer(matchVersion, reader);
        src.setMaxTokenLength(maxTokenLength);
        src.setReplaceInvalidAcronym(replaceInvalidAcronym);
        TokenStream tok = new StandardFilter(matchVersion, src);
        tok = new LowerCaseFilter(matchVersion, tok);
        tok = new StopFilter(matchVersion, tok, stopwords);
        return new TokenStreamComponents(src, tok) {
            @Override
            protected boolean reset(final Reader reader) throws IOException {
                src.setMaxTokenLength(StandardAnalyzer.this.maxTokenLength);
                return super.reset(reader);
            }
        };
    }
}
